HYPOTHESIS: We hypothesize that the physiologic neuroendocrine counter regulatory responses to exercise will be significantly attenuated in patients w/Type I diabetes if these subjects have been exposed to episodes of hypoglycemia in the preceding 24 hours. We also hypothesize that the physiologic neuroendocrine counter regulatory responses to hypoglycemia will be significantly attenuated in patients w/Type I diabetes if these subjects have undergone prolonged physical exercise in the preceding 24 hours. SPECIFIC AIMS: 1) To determine the effect/s of antecedent moderate hypoglycemia on the neuroendocrine, autonomic nervous system and metabolic counter regulatory responses to subsequent prolonged exercise in patients w/Type I diabetes. 2) To determine the effect/s of antecedent prolonged exercise on the neuroendocrine, autonomic nervous system and metabolic counter regulatory responses to subsequent moderate hypoglycemia in patients w/Type I diabetes.